Today's magnetic card key systems are popular with hotels and resorts because they're flexible and cheap. The door lock systems run off batteries in stand-alone mode -- no power or data links are needed. Operation is simple. Keys can easily be replaced. The door lock is smart enough to store information about who has accessed the room and at what times, leaving an audit trail for security personnel. And the systems are self-maintaining as long as the battery lasts. It simply rolls forward to the next lock combination each time a new key is entered or the current one expires. However, the lock mechanism itself cannot be updated or reconfigured without visiting the room.

Electronic lock companies and hotels are experimenting with other security key devices, including biometric fingerprint readers, smart cards, and proximity cards that allow the guest to unlock the door without touching the lock. Vendors are also experimenting with infrared and other wireless technologies.

Proximity card readers haven't been well received because they can be used to track where guests are in the hotel at any given time. Experimental systems have been deployed where an RFID chip was embedded in frequent-guest cards, says Brian Garavuso, CIO at Hilton Grand Vacations Co. and chairman of the American Hotel and Lodging Association's technology committee. "[Guests] were uncomfortable with us knowing where they were at any given time," he says. "It didn't go beyond the conceptual stages."

Glenn Peacock, director of marketing at lock system vendor Saflok in Troy, Mich., says his company's door locks can be used with memory cards and smart cards as well as with magnetic stripe cards. However, biometric fingerprint readers have been a bust so far. These systems read a fingerprint when the guest checks in and generate a unique algorithm that's used to authenticate the user and open the door. Although no thumbprint data is stored, he says users don't like the idea of being fingerprinted. "The American society is reluctant to have their fingerprints scanned," he says.

Cost and ease of support are two of the biggest factors to consider when choosing a door lock system, says Jocelynn Lane, vice president at VingCard AS in Norway.